Conventional DC power-supply devices are known that have an inverter as a load, with the invertor driving a compressor motor used in an air conditioner, a heat-pump water heater, a refrigerator, and a freezer, that are connected to the load, and that convert an alternating current into a direct current. Patent Literature 1, for example, discloses a DC power-supply device that can convert a single-phase alternating current into a direct current and can boost the output voltage with a simple configuration.